Aerosol paints using conventional solvent reduced pigmented organic polymeric binders have found wide acceptance because of their ready availability to apply paint coatings without concomitant clean up problems associated with brushing applications and brush-marks foreign to spray coating applications. Until recently, aerosol paints were substantially and conventionally water-free, solvent thinned products formulated with propellants of the fluorochlorohydrocarbon class. Concern over flourinated hydrocarbon propellants in the atmosphere gave impetus to use of non-halogenated (non-fluorinated) propellants, primarily low molecular weight hydrocarbons such as butane, propane, hexane, heptane, etc., which are flammable.
With rapid development of water-reducible paint systems characterized by ease of application, ready clean up, and freedom from fire hazard, water-containing systems for aerosol paints are of major interest. Water-containing aerosol spray paints have the advantage of low toxicity levels, noncombustible spray paint systems, and in some cases ready clean up with soap and water after completion of the paint application.
The following patents are of interest in the development of the aerosol paint art and the present invention:
Howard U.S. 4,187,204, takes advantage of resinous synthetic polymers or paint binders; illustratively, maleinized oils, oil modified alkyds, copolymer oils, epoxy resins, etc., having sufficient carboxyl groups (acid value) to be solubilized in water by neutralization of the acid groups present. Howard's product may contain some water, but not more than 10%. Acid values of the resins were neutralized with ammonia and amines, and dissolved in water-soluble solvents. Howard includes as propellants the lower molecular weight hydrocarbons flourocarbons, etc., CO.sub.2, nitrous oxide, cyclo-propane, etc. Among the host of non-distinguishable propellants dimethyl ether was named as useful. The useful water content was limited however to preferably less than 8%.
Broadhead U.S. Pat. No. 2,985,602 teaches the concept of producing a low molecular weight alkyd resin having an acid value between 6 and 25, made water-dispersible by neutralization with lithium hydroxide.
Vasishth et al U.S. Pat. No. 4,240,940 teaches an aerosol paint which is capable of being cleaned up with water containing from 8%, but preferably less than 1% of water in which the binder vehicle solids are a water-reducible alkyd resin dissolved in a solution of Butyl Cellosolve and n-butanol. Other solvents for the water-reducible alkyd are ethylene glycol monobutyl ether, Butyl Carbitol and V. M. & P. Naptha.
Howard U.S. Pat. No. 4,125,499 uses organic co-solvents including acetone, ethers, ethylene glycol n-butyl ether, etc., with about 5% of water with some water-soluble alkyd resins (Aquamac 1200, Kelsol 3902, etc). Aliphatic hydrocarbons and halofluorocarbons and methyl ethers including dimethyl ether are used in propellant admixtures. Again water is limited to not more than 10%.
Suk U.S. Pat. No. 4,265,797 teaches manufacture of an aerosol paint requiring water-miscible propellants, dimethyl ether. The resins disclosed appear to be very similar to those disclosed in U.S. Pat. No. 2,795,564 (Rohm and Haas).
Rotheim U.S. Pat. No. 1,892,750 teaches use of dimethyl ether among other propellants for dispensing a spray of liquid from a pressurized container.
Attention is also directed to a Suk Belgium patent No. 890,564 of Jan. 18, 1982 which contains from 10-50% water and from 0-50% dimethyl ether and another propellant in conjunction with up to 45% polar organic co-solvents in an aqueous aerosol paint system.